The present invention relates to a damper for furniture, especially for hinges, comprising a housing in which a piston connected to a piston rod is received so that it can be displaced, where a fluid flows through a flow channel on or in the piston during a movement of the piston inside the housing and a different damping power is obtained during movement of the piston in different directions, where the cross-section of the flow channel can be modified in some sections on at least one groove in which a plate can be moved relative to the piston.
Known from WO 2007/099100 is a damper for furniture in which a piston is displaceable in a cylindrical housing. The housing is filled with a fluid so that during a movement of the piston, damping of a movement takes place, where the damping forces are different depending on the direction of movement of the piston. For this purpose a plate which is movable relative to the piston is provided, by means of which the cross-section of a flow channel can be modified on a groove.
Such a damper has proved successful per se but the flow velocity of the fluid in the flow channel is very high. Specifically during rapid movements of a furniture part, high peak loads can act on the damper. As a result, cavitation can occur in the damper as a result of appreciable pressure differences.
It is therefore the object of the present invention to provide a damper for furniture in which high peak loads can be accommodated without the risk of cavitation.
This object is achieved with a damper having the features of claim 1.
According to the invention a substantially funnel-shaped outlet is formed on the at least one groove and/or the groove has a section disposed at an angle in the radial direction to avoid cavitation. Due to the funnel-shaped outlet a funnel-shaped transition can be provided in the area of the transition between the groove and a flow channel in the axial direction so that the flow velocity is no longer abruptly reduced but is gradually reduced in this transition zone due to expansion of the cross-section. This funnel-shaped transition has the effect that the fluid no longer flows abruptly but with a gentle transition into the flow channel in the axial direction of the piston. This improves the velocity and pressure relationships to avoid cavitation. In addition, it is possible to provide the groove with a section disposed at an angle to the radial direction. As a result, the groove can be lengthened compared with its purely radial extension so that the throttle effect of the groove is distributed over a longer distance and the groove can thus be configured to be larger in cross-section. This measure also reduces the tendency to cavitation since somewhat lower flow velocities are achieved as a result of the larger cross-section of the groove.
In a preferred embodiment of the invention, the groove has a bent section. In this case, the groove can be configured to be wavy or spiral-shaped. Due to this measure, the groove can be lengthened compared with its purely radial extension so that the throttle effect of the groove is distributed over a longer distance and the groove can thus be configured to be larger in cross-section. The groove can have a length of at least 0.5 to 15 mm in this case, which is relatively long compared with the usual diameter of a piston.
In a further embodiment the funnel-shaped outlet has rounded transitions. As a result, the funnel-shaped outlet is configured to be funnel-shaped so that a particularly gentle transition is made from the throttle gap of the groove. The funnel-shaped outlet is preferably disposed adjacent to an axial flow channel of the piston since the cavitation occurs particularly at the transition between the throttle gap and the axial flow channel.
The damper can be configured both as a pressure and as a tension damper. However it is pressure dampers which can be loaded as a result of their design.
The invention is explained in detail hereinafter by two exemplary embodiments with reference to the appended drawings.